It was eye-wateringly expensive and required a high-end system, though. It was good, and I liked it too, but it's not the same as being usable from pretty much anywhere for $0.
I was using Apple Notes for some “math thinking” the other week. A killer feature for me would be an easy way to input various math Unicode characters (I was just copy and pasting them).
Pretty cool. It looks like it also uses local storage - so if you navigate away and come back (or just refresh the page) all of your expressions are still there. A lot of paid productivity apps that I use don't even manage that.
[0] - https://writings.stephenwolfram.com/2013/06/there-was-a-time...
https://instacalc.com/
https://www.inftyproject.org/en/software.html
(I used to use the math input palette w/ a Wacom ArtZ on my NeXT Cube for transcribing math documents in college)
I still like it better than the math built into notes for anything beyond basics.